speedometer pickup is it the right one??

[mcarlito]

Hello,<br />I have a 1962 Crestliner 14'-0" with the original speedometer on it and when I put compressed air into the tube, it works fine. Now when I hook up the tube to the pickup, which is located about left center about 8 inches and placed to the correct depth, and I go for a spin, at wot throttle it reads 10MPH. Could it be that the speedometer needs a different pickup??<br />Thanks for the input, we are enjoying this boat very much, got my two boys up on skis for the first time and they love it. <br /><br />Mike

 

[angus63]

Re: speedometer pickup is it the right one??

Hey huge<br />if its a pitot tube type pickup, they work via VACUUM, not pressure. Pressurizing the gage may of damaged the mechanism. If its a paddlewheel type, nevermind.<br />The pitot tube and tubing can be purchased separately if they are the cause of the misread. Note that these speed devices are notoriously innaccurate and often not repeatable due to leaks and clogs. I much prefer a GPS.

 

[mcarlito]

Re: speedometer pickup is it the right one??

Thanks angus63 it is a pitot tube type pickup and the tube and pitot are new, it's the speedometer that's original, and I didn't put much air into it, I used a can of compressed not a full blown compressor. I now understand it works via vacuum, not pressure. If that's the case, does the pitot work like that??<br />Thanks again<br />Mike

 

[angus63]

Re: speedometer pickup is it the right one??

Yep. The velocity of the water passing the opening of the pitot creates a vacuum. More velocity, more vacuum. It is imperative that there be absolutely no leaks from the pitot to the gage or it will be useless.<br />Good luck

 

[Silvertip]

Re: speedometer pickup is it the right one??

Ummm - I think ya got it backwards Angus. Pitot speedos work on water pressure acting against air. Pull the tube off the speedo head while under way and you'll get wet feet. The opening in the pitot pickup points forward. I guess the proof is that when the poster applied pressure to the tube the speedo registered normally. If it sucked vacuum, the needle would be sucked against the peg.